diff options
| author | Oleg Nesterov <oleg@redhat.com> | 2024-05-12 08:02:07 -0700 |
|---|---|---|
| committer | Paul E. McKenney <paulmck@kernel.org> | 2024-07-04 13:48:57 -0700 |
| commit | 6f4cec22c38a33c1981e8f39cdc698119903f1cb (patch) | |
| tree | 35a8f168a32cf55caee5efaa3b6276c6fe9ec515 /kernel | |
| parent | 7f09e70f9eae95b12488b931ee249f36e35df542 (diff) | |
rcu: Eliminate lockless accesses to rcu_sync->gp_count
The rcu_sync structure's ->gp_count field is always accessed under the
protection of that same structure's ->rss_lock field, with the exception
of a pair of WARN_ON_ONCE() calls just prior to acquiring that lock in
functions rcu_sync_exit() and rcu_sync_dtor(). These lockless accesses
are unnecessary and impair KCSAN's ability to catch bugs that might be
inserted via other lockless accesses.
This commit therefore moves those WARN_ON_ONCE() calls under the lock.
Signed-off-by: Oleg Nesterov <oleg@redhat.com>
Signed-off-by: Paul E. McKenney <paulmck@kernel.org>
Diffstat (limited to 'kernel')
| -rw-r--r-- | kernel/rcu/sync.c | 12 |
1 files changed, 4 insertions, 8 deletions
diff --git a/kernel/rcu/sync.c b/kernel/rcu/sync.c index 6c2bd9001adc..da60a9947c00 100644 --- a/kernel/rcu/sync.c +++ b/kernel/rcu/sync.c @@ -122,7 +122,7 @@ void rcu_sync_enter(struct rcu_sync *rsp) * we are called at early boot time but this shouldn't happen. */ } - WRITE_ONCE(rsp->gp_count, rsp->gp_count + 1); + rsp->gp_count++; spin_unlock_irq(&rsp->rss_lock); if (gp_state == GP_IDLE) { @@ -151,15 +151,11 @@ void rcu_sync_enter(struct rcu_sync *rsp) */ void rcu_sync_exit(struct rcu_sync *rsp) { - int gpc; - WARN_ON_ONCE(READ_ONCE(rsp->gp_state) == GP_IDLE); - WARN_ON_ONCE(READ_ONCE(rsp->gp_count) == 0); spin_lock_irq(&rsp->rss_lock); - gpc = rsp->gp_count - 1; - WRITE_ONCE(rsp->gp_count, gpc); - if (!gpc) { + WARN_ON_ONCE(rsp->gp_count == 0); + if (!--rsp->gp_count) { if (rsp->gp_state == GP_PASSED) { WRITE_ONCE(rsp->gp_state, GP_EXIT); rcu_sync_call(rsp); @@ -178,10 +174,10 @@ void rcu_sync_dtor(struct rcu_sync *rsp) { int gp_state; - WARN_ON_ONCE(READ_ONCE(rsp->gp_count)); WARN_ON_ONCE(READ_ONCE(rsp->gp_state) == GP_PASSED); spin_lock_irq(&rsp->rss_lock); + WARN_ON_ONCE(rsp->gp_count); if (rsp->gp_state == GP_REPLAY) WRITE_ONCE(rsp->gp_state, GP_EXIT); gp_state = rsp->gp_state; |